Top 10 Methods for Java Arrays
2013-09-30 09:13
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The following are top 10 methods for Java Array. They are the most voted questions from stackoverflow.
0. Declare an array
1. Print an array in Java
2. Create an ArrayList from an array
3. Check if an array contains a certain value
4. Concatenate two arrays
5. Declare an array inline
6. Joins the elements of the provided array into a single String
7. Covnert an ArrayList to an array
8. Convert an array to a set
9. Reverse an array
10. Remove element of an array
One more – convert int to byte array
0. Declare an array
String[] aArray = new String[5]; String[] bArray = {"a","b","c", "d", "e"}; String[] cArray = new String[]{"a","b","c","d","e"};
1. Print an array in Java
int[] intArray = { 1, 2, 3, 4, 5 }; String intArrayString = Arrays.toString(intArray); // print directly will print reference value System.out.println(intArray); // [I@7150bd4d System.out.println(intArrayString); // [1, 2, 3, 4, 5]
2. Create an ArrayList from an array
String[] stringArray = { "a", "b", "c", "d", "e" }; ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(stringArray)); System.out.println(arrayList); // [a, b, c, d, e]
3. Check if an array contains a certain value
String[] stringArray = { "a", "b", "c", "d", "e" }; boolean b = Arrays.asList(stringArray).contains("a"); System.out.println(b); // true
4. Concatenate two arrays
int[] intArray = { 1, 2, 3, 4, 5 }; int[] intArray2 = { 6, 7, 8, 9, 10 }; // Apache Commons Lang library int[] combinedIntArray = ArrayUtils.addAll(intArray, intArray2);
5. Declare an array inline
method(new String[]{"a", "b", "c", "d", "e"});
6. Joins the elements of the provided array into a single String
// containing the provided list of elements // Apache common lang String j = StringUtils.join(new String[] { "a", "b", "c" }, ", "); System.out.println(j); // a, b, c
7. Covnert an ArrayList to an array
String[] stringArray = { "a", "b", "c", "d", "e" }; ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(stringArray)); String[] stringArr = new String[arrayList.size()]; arrayList.toArray(stringArr); for (String s : stringArr) System.out.println(s);
8. Convert an array to a set
Set<String> set = new HashSet<String>(Arrays.asList(stringArray)); System.out.println(set); //[d, e, b, c, a]
9. Reverse an array
int[] intArray = { 1, 2, 3, 4, 5 }; ArrayUtils.reverse(intArray); System.out.println(Arrays.toString(intArray)); //[5, 4, 3, 2, 1]
10. Remove element of an array
int[] intArray = { 1, 2, 3, 4, 5 }; int[] removed = ArrayUtils.removeElement(intArray, 3);//create a new array System.out.println(Arrays.toString(removed));
One more – convert int to byte array
byte[] bytes = ByteBuffer.allocate(4).putInt(8).array(); for (byte t : bytes) { System.out.format("0x%x ", t); }
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